Conformational changes and dynamic rheological properties of fish sarcoplasmic proteins treated at various pHs

Panchaporn Tadpitchayangkoon, Jae W. Park, Jirawat Yongsawatdigul

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40 Citations (Scopus)

Abstract

The conformational changes and rheological properties of soluble sarcoplasmic proteins isolated from striped catfish (Pangasius hypophthalmus), treated at various pHs (2-12), were investigated. Isoelectric point of striped catfish sarcoplasmic proteins was determined to be pH 5. SDS-PAGE of sarcoplasmic proteins treated at various pHs, showed molecular masses ranging from 11 to 97 kDa. Most sarcoplasmic proteins, regardless of treated pHs, showed a molecular mass of 43 kDa. A decrease in total sulfhydryl content was observed when the pH was shifted away from 6, indicating disulfide formation at pH lower and higher than 6. Gradual increases of S0-ANS and S0-PRODAN were observed as pH increased from 6 to 12, indicating the unfolding of sarcoplasmic proteins during alkaline extraction. DSC thermograms of sarcoplasmic proteins treated at pH 5-9 exhibited an exothermic transition peak, probably due to disulfide bond formation, and/or hydrophobic interactions, which was highly related to the onset temperature of G′ rising. Gel network formation of sarcoplasmic proteins did not take place at extreme pHs (<4 or >9) where proteins were highly charged while the viscoelastic properties of sarcoplasmic proteins were observed at pH 5.5-9. The highest G′ value at 90 °C was observed at pH 5.5 and 8 (P ≤ 0.05). The gel point, a temperature at which G′ = G″, increased to higher temperature as pH was shifted away from 7.

Original languageEnglish
Pages (from-to)1046-1052
Number of pages7
JournalFood Chemistry
Volume121
Issue number4
DOIs
Publication statusPublished - 2010 Aug 15

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Keywords

  • DSC
  • Dynamic rheological properties
  • Sarcoplasmic proteins
  • Striped catfish
  • pH

ASJC Scopus subject areas

  • Analytical Chemistry
  • Food Science

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